Cooled piston for internal combustion engines

ABSTRACT

The invention relates to a piston for internal combustion engines whose piston head presents an annular cooling channel which on its end open towards the piston shaft is closed off by an appropriately shaped wall element which is radially divided in at least one place. The aim of the invention is to improve heat dissipation in such a piston. To this end the periphery of the wall element is provided with several radially arranged, evenly distributed transverse walls which extend axially into the cooling channel.

CROSS REFERENCE TO RELATED APPLICATIONS

Applicant claims priority under 35 U.S.C. §119 of German Application No.199 26 568.2 filed Jun. 11, 1999. Applicant also claims priority under35 U.S.C. §120 of PCT/DE00/01169 filed Apr. 14, 2000. The internationalapplication under PCT article 21(2) was not published in English.

The invention relates to a cooled piston for internal combustion engineswith the features specified in the introductory part of claim 1.

Such pistons are known from DD 252 638 A1 and DE 41 34 530 A1, inconnection with which the part of the wall serving for covering thedownwardly open, ring-shaped cooling channel extending all around isrealized in the form of an open sheet metal ring. Making use of itselastic deformation according to the Seeger ring principle, i.e. withinitial tension in the radial direction, said ring is inserted in agroove extending on the inner circumference of the piston ring zone orouter circumference of the wall of the combustion chamber.

A piston crown part is known DE 42 08 037 C2 in connection with whichthe downwardly open cooling channel is covered by a fixed, tensioned cupspring. Said spring is divided in at least two parts and radially restsfreely on the inside and outside against abutments on axially opposedsides.

A piston with a cooling channel in the crown of the piston is known fromDE 39 91 677 T1, in connection with which provision is made for a baffleplate covering the lower open end of the cooling channel. The ends ofsaid baffle plate are vertically bent off upwards in the zone ofdivision in order to maintain a defined level of cooling oil in thecooling channel.

The drawback with the above embodiments is that the dwelling time of thecooling oil in the cooling channel has not been solved in a satisfactorymanner to the desired extent.

Therefore, the invention is based on the problem of prolonging thedwelling time of the cooling oil in the cooling channel and to reinforcethe Shaker effect of the cooling oil in order to achieve superior heatdissipation in the zones of the piston to be cooled.

Said problem is solved in connection with a piston of the type specifiedabove by the features according to the characterizing part of claim 1.

Other useful variations according to the invention are contained in thedependent claims.

The invention is explained in greater detail in the following with thehelp of exemplified embodiments shown in the drawing, in which:

FIG. 1 is a sectional side view of a piston crown.

FIG. 2 shows a bottom view of FIG. 1, the left half according to sectionII—II, the right half according to section III—III.

FIG. 3 is an enlarged representation of the view X of FIG. 1.

FIG. 4 is a partial view of a wall element according to the inventionbefore it has been reshaped.

FIG. 5 is a partial view of the wall element after it has been reshaped.

FIG. 6 is a partial view (layout) of another embodiment of the wallelement before it has been reshaped.

FIG. 7 is a partial view of a wall element with a feed opening for thecooling oil.

FIG. 8 is a side view according to FIG. 7.

FIG. 9 is a partial view of another embodiment according to sectionIX—IX; and

FIG. 10 is a top view according to FIG. 9.

A cooled piston is comprised of a piston crown 1 and a piston shaft (notdrawn). Said shaft is connected with said piston crown in a hingedmanner via a piston pin (not shown). In the piston crown 1, provision ismade for a cooling channel 2 extending all around in the form of a ring.Said cooling channel is closed at its end that is closed toward thepiston shaft, by a wall element 3, for example a cup spring divided intwo parts, or in two sheet metal strip halves 4, 5. In order to prolongthe dwelling time of the cooling oil in the cooling channel 2 and toachieve in this way superior dissipation of the heat from the zones ofthe piston to be cooled, the wall element 3 is provided with a pluralityof the radially arranged transverse walls 6. Said transverse walls aredistributed over the periphery of said wall element and axially extendinto the cooling channel 2, so that defined Shaker chambers are formedin this manner. The wall element 3 is supported in the piston crown inthe manner known per se, such as for example by providing an abutment 7for the inner periphery and a corresponding collar-like recess 8 for theouter periphery of the wall element 3. The wall element 3 is divided bythe radial divisions 9, 10 in the two metal sheet strip halves 4, 5,which, under initial tension, form the lower termination of the coolingchannel 2. For feeding cooling oil, two part pieces 11, 12 in the firstsheet metal half 4, which are bent off upwards in an inclined manner,are disengaged in such a manner that the jet of cooling oil is divided,causing about one half of the oil jet to enter the cooling channel 2 inthe one direction and the other half in the opposite direction.

The flow of oil then circulates peripherally in the cooling channel andis discharged again by way of a discharge opening 13 provided in thesecond half 5 of the sheet metal strip.

Following said path from the inlet into to the outlet from the coolingchannel 2, the flow of oil is brought into contact with the piston zonesto be cooled a number of times in a Shaker-like manner by the transversewalls 6, which form a type of chambers, and also due to the movement ofstroke of the piston, so that good heat transfer from said zones intothe cooling oil is achieved.

The transverse walls 6 of the wall element 3 can be produced in a simplemanner by reshaping them. Such re-forming can be based, for example on aring-shaped, punched-out plane wall element 3, or a straight plane wallelement 3, whereby the folding 14 has to be produced in connection withthe straight starting strip in such a manner that a ring-shaped wallelement 3 is subsequently obtained.

In another embodiment, a deepening 16 is produced by molding in thedirection of the piston shaft for enlarging the Shaker chamber in theplane area 15 of the wall element 3.

With such an embodiment, superior heat dissipation is, achieved in apiston with a cooling channel in a constructively simple manner.

What is claimed is:
 1. A cooled piston for internal combustion enginescomprising a cooling channel extending all around in the piston crown,whereby the cooling channel is closed at its end that is open toward thepiston shaft, by a correspondingly shaped wall element, said wallelement being secured on the piston and being radially divided at leastonce, wherein the wall element is provided with a plurality of radiallyarranged transverse walls distributed over its periphery and axiallyextending into the cooling channel and with part pieces bent off upwardsin an inclined manner and disengaged from the wall element, each of saidpieces extending in an approximately S-shaped form.
 2. The cooled pistonaccording to claim 1, wherein the transverse walls form one piece withthe wall element.
 3. The cooled piston according to claim 1, wherein thetransverse walls are produced by reshaping a wall element comprising ametal sheet, which is planar in its original state.
 4. A cooled pistonfor internal combustion engines comprising a cooling channel extendingall around in the piston crown, whereby the cooling channel is closed atits end that is open toward the piston shaft, by a correspondinglyshaped wall element, said wall element being secured on the piston andbeing radially divided at least once, wherein the wall element isprovided with a plurality of radially arranged transverse wallsdistributed over its periphery and axially extending into the coolingchannel and a deepening is molded in the direction of the piston shaftin a planar area between two transverse walls.